Inorg. Chem. 1993, 32, 5646-5651
5646
Articles Osmium(V1) Complexes of Tetrathiotungstate Patricia A. Shapley,' Zewdu Gebeyehu, Naijie Zhang, and Scott R. Wilson School of Chemical Sciences, University of Illinois, Urbana, Illinois 6 1801 Received February I I, 1993' The anionic organoosmium complexes [Y] [Os(N)R2C12] (Y = PPh4, NBu4; R = CH3, CH2SiMe3) reacted with (NH&WS4 or (NH4)2MoS4 to give the heterobimetallic complexes [Y] [Os(N)R2(p-S)2MS2] (M = W, Mo). The reaction of [Os(N)(CH2SiMe3)2C1]2 with an excess of (NH4)2WS4 in CHzCl2 at room temperature produced a trimetallic complex in which two organonitridoosmium units are bridged by a tetrathiotungstate group, (Me3S~CH~)~(N)OS(~-S)~W(~-S)~O~(N)(CH~S~M~~)~. The molecular structures of [NBu,] [Os(N)(CH2SiMe3)2(pS)2WS2] and [(Me3SiCH2)2(N)Os]2(p-WS4) were determined by X-ray diffraction. Crystals of [NBy] [Os(N)(CH2SiMe3)2(p-S)~WS2]are monoclinic in space group C2/c with a = 39.358(9) A, b = 11.074(3) A, c = 18.685(9) A, 0 = 109.37(3)O, Z = 8, R = 0.040, and R, = 0.048. Crystals of [(Me3SiCH2)2(N)0sl2(p-WS4) are triclinic in space group PT with (I = 10.012(3) A, b = 11.979(5) A, c = 15.775(4) A, 01 = 105.51(3)0, 0 = 97.34(2)O, y = 112.03(3)O, 2 = 2, R = 0.026, and R, = 0.030. The reaction between [(Me3SiCH2)2(N)Os]2(p-WS4) and Ph4PCl gave [PPh412[R20s(N)Cl12(~WS,).
Introduction Polymetallic sulfides have attracted the attention of the chemical community because of their applications in catalysis, their solid-state properties, and their relevance to iron-sulfur metalloenzymes.' One method for the synthesis of polymetallic sulfides is the reaction between tetrathiometalates and transition metal coordination compounds. The tetrathiomolybdate and tetrathiotungstate anions, M0s.4~and WSd2-,coordinate very well to a variety of transition metals due to the excess electron density on the sulfur atoms and the accessibleemptyorbitalson the molybdenum and tungsten atoms.2 The molecular structures of these inorganic coordination compounds usually show the tetrathiometalate moiety chelating to a metal through two sulfur bridges, as in S2W(~-S)zCo(bpy)2~ or [PPh4]2[(S2W(p-S)2)2Fe(DMF)2],4 or bridging two transition metals with all four sulfur atoms, as in [PPh4]2[C12Fe(p-S)2W(pc-S)2FeC12].SOther bonding modes are known but are less common. Recently, organometallic tetrathiometalate complexes were prepared. The organometallic fragments are in relatively low oxidation states and contain r-acceptor diene, arene, cyclopentadienyl, or carbonyl ligands.613 The tetrathiometalate moiety seems to be rather unreactive in these complexes, but con-
* Abstract published in Advance ACS Abstracts, November 1, 1993. (1) (a) Gates, B. C. Catalytic Chemistry;John Wiley & Sons: New York, 1991; pp 406-422. (b) Iron-Sulfur Proteins; Spiro, T. G . , Ed.; John Wiley & Sons: New York, 1982. (c) Metalloproteins, Chemical Properties and Biological Effects; Otsuka, S.,Yamanaka, T., Eds.; Elsevier: New York, 1988. (2) Miiller, A.; Diemann, E.; Joetes, R.; BBgge, H. Angew. Chem., Int. Ed. Engl. 1981, 20, 934-955. (3) Muller, A,; Joetes, R.; Flemming, V.;Potthast, R. Inorg. Chim. Acta 1980,44, L33-L3S. (4) Stremplc, P.; Baenziger, N. C.; Coucouvanis, D. J . Am. Chem. SOC. 1981,103,4601-4603. ( 5 ) Coucouvanis, D.; Simhon, E. D.; Stremple, P.; Ryan, M.; Swenson, D.; Baenziger, N. C.; Simopolous, A,; Papaefthymiou, V.;Kostikas, A.; Petrouleas, V. Inorg. Chem. 1984, 23, 741-749. (6) Mizobe, Y.; Hosomizu, M.; Kawabata, J.; Hidai, M. J . Chem. SOC., Chem. Commun. 1991, 1226-1227. (7) Massa, M. A.; Rauchfuss, T. B.; Wilson, S.R. Inorg. Chem. 1991,30, 46614669. (8) Howard, K. E.; Lockemeyer, J. R.; Massa, M. A.; Rauchfuss, T. B.; Wilson, S. R.; Yang, X . Inorg. Chem. 1990,29, 4385-4390. 0020-166919311332-5646$04.00/0
version of the coordinated tetramethylbutadiene ligand in [(C4Med)NiC1]2WS4to free tetramethylthiophene has been reported by Rauchfuss.8 We have previously prepared organoosmium(V1) complexes of perrhenate,14 chromate,lS and tungstate.l6 We recently extended this work to include heterometallic complexes containing tetrathiomolybdate and tetrathiotungstate. Here we report the synthesis, characterization, and reaction chemistry of some of these.
Results S y n W i of Tetrathiotmgstate andMolybdate Complexes. The reaction of trans-[NBun4][Os(N)(CHzSiMe3)2Clz] with 1 equiv of (NH4)2WS4produced the osmium tetrathiometalate complex [NBun4][Os(N)(CH2SiMe3)2WS4] (1)" (Scheme I). Theyellow product crystallizedfrom methylenechloride/hexane in 8 1%yield. Themethylcomplex [PPh] [Os(N)(CH3)2WS4] (2) wasprepared in an analogous manner from [PPh,] [Os(N)(CH3)2C12] and the tetrathiotungstate salt. These complexes were characterized by spectroscopic techniques and elemental analysis. They are thermally stable, stable to air, and soluble in organic solvents. The lH NMR spectrum of 1 shows two doublets at 6 3.17 and 2.16 for the diastereotopic methylene protons and a singlet at 6 4 - 0 2 for equivalent methyl protons of the (trimethylsily1)methyl ligand. The lH NMR spectrum of the methylosmium complex, 2, has a single resonance at S 2.61 for the equivalent methyl groups. The infrared spectra of both complexes display a strong band near 1105 cm-1 and a (9) Howard, K. E.; Rauchfuss, T. B.; Wilson, S.R. Inorg. Chem. 1988,27, 1710-1716. .. . .. (10) Howard, K. E.; Rauchfuss, T. B.; Rheingold, A. L. J . Am. Chem. SOC. 1986, 108,291-299. (1 1) Adam, G. J. S.; Green, M. L. H. J . Organomet. Chem. 1981,208,299znx (12) Ruffing, C. J.; Rauchfuss, T. B. Organometallics 1982, I, 400401. (13) Rosenheim, L. D.; McDonald, J. W. Inorg. Chem. 1987,26,3414-3416. (14) Zhang, N.; Shapley, P. A. Inorg. Chem. 1988, 27, 976-977. (15) Zhang, N.; Mann, C.; Shapley, P. A. J. Am. Chem. Soc. 1988, 110, 65916592. (16) Zhang, N. Ph.D. Thesis, University of Illinois, 1991. (17) The synthesis and reaction chemistry of 1 have been reported in a preliminary communication: Shapley, P. A.; Zhang, N. J. Am. Chem. SOC.1993, 115, 7866-7867. ~
0 1993 American Chemical Society
Inorganic Chemistry, Vol. 32, No. 25, 1993 5647
Osmium(V1) Complexes of Tetrathiotungstate Scheme I
I
R = CH,
3
Scheme I1
/
Si \
(.*.'
very strong band near 500 cm-l that can be assigned to the osmium-nitrogen and terminal tungsten-sulfido stretching vibrations, respectively. The FAB mass spectrum of 1 exhibits a peak assigned to the tetrabutylammonium cation ( m / z = 242) in the positive-ion mode and a peak assigned to [Os(N)(CH2SiMe&WS4]- ( m / z = 692) in the negative-ion mode. The pattern of isotope abundance in the parent anion is identical to thecalculated pattern. The UV-visible spectra includean intense absorption at 372 nm for the ligand-metal charge-transfer band of the tetrathiotungstate unit in both complexes. The cyclic voltammogram of 1 shows only irreversible waves: a reduction at -1.15 V and an oxidation at 1.20 V in acetonitrile. The reaction between [NBu"] [Os(N)(CH~SiMe3)zC121and finely ground (NH&MoS4 in acetonitrile produced the osmiumtetrathiomolybdatecomplex [NBun4][Os(N)(CH2SiMe3)2MoS4] (3). After crystallization of the crude product from methylene chloride/hexane, 3 was obtained in 50% yield as analytically pure brown crystals. The IH N M R spectrum of [NBu"][Os(N)(CH2SiMe3)2MoS4] is very similar to that of [NBun4][Os(N)(CHzSiMe3)2WS4] with two doublets at 6 3.01 and 2.59 for the diastereotopic methylene protons and a singlet at 6 -0.03 for the trimethylsilyl group. The IR spectrum of 3 includes a strong band at 1100cm-1 due to the osmium-nitrido unit and two bands at 5 17 and 503 cm-1 due to molybdenum-sulfur stretching vibrations. The UV-visible spectrum includes a strong band for the tetrathiomolybdate unit at 436 nm, corresponding to ligandto-metal charge transfer of the tetrathiomolybdate unit. A minor product in thereaction between [NBun4][Os(N)(CHzSiMe&Clz] and (NH4)zWSd was (Os(N)(CH,SiMe,)z~z(cLWS4). The trimetallic compound, 4, was prepared in better yield by treatment of [Os(N)(CH2SiMe3)2C1]2 with an excess quantity of (NH4)2WS4 in methylene chloride. The yellow product was
formed nearly quantitatively by 1H NMR, but due to its high solubility in all organic solvents, we could obtain it only in up to 56% yield as analytically pure yellow crystals from cold hexane solutions. The lH NMR spectrum of 4 clearly shows two, inequivalent (trimethylsily1)methyl groups with well-resolvedsinglets at 0.06 and 0.10 ppm for the trimethylsilyl moieties and four doublets between 3.70 and 3.17 ppm for the methylene protons. The IR spectrum of 4 displays bands at 1102 and 466 cm-I that can be assigned to osmium-nitride and tungsten-sulfide vibrations, respectively. The FAB-MS showed an intense molecular ion peak at m / z = 1070. The UV-visible spectrum of 4 includes a band at 392 nm for the tetrathiotungstate group. Cyclic voltammetry in CHzClz shows a reversible reduction at -0.83 V vs SCE. Molecular Structureof [Nsun410S(N)(~giMe,)~WS,]. The molecular structure of 1 was determined by X-ray diffraction. Two sulfur atoms bridge a tetrahedral tungsten atom and a distorted square pyramidal osmium center (Figure 1). Crystallographic parameters are shown in Table 111, and selected bond distances and angles are shown in Table I. The osmium atom is above the plane of the four basal ligands. This is commonly observed in five-coordinate nitridoosmium complexes. The nitrogen-osmium-sulfur angles are greater than the nitrogenosmium-carbon angles. This is probably due to repulsion between lone pairs on the nitride and the bridging sulfides. The osmiumnitrogen distance and the average osmiumsarbon distance in [NBun4][Os(N)(CH2SiMe3)~WS4] are 1.62(1) and 2.12 A, respectively. The average terminal W=S distance is 2.13 A, while the average bridging W-S distance is 2.241 A. The osmium-tungsten distance of 2.897 A is shorter than the sum of the covalent radii. Molecular Structure of [(Me&iCHz)~&(N)h(p-WS4). The
5648 Inorganic Chemistry, Vol. 32, No. 25, 1993
Shapley et al.
n
Table 111. Crystal Data Collection and Refinement Parameters 4
1
~~
OSWS~S~ZNZCZ~H~S C~~H~~S~~NZS~OS~W 933.20 39.358(9) 11.074(3) 18.685(9)
7,deg
v,A3
1069.38 10.012(3) 11.979(5) 15.775(4) 105.5l(3) 109.37(3) 97.34(2) 112.03(3) 7683(10) 1634(3) . 8 2 C2/c (No. 15) Pi (No. 2) 26 OC -75 O C M OKu;‘ A(Ka1) = 0.709 30, A(Ka2) 0.713 59, X(Ka) 0.710 73 1.613 2.173 66.50 0.040 0.048
117.53 0.026 0.030
Graphite crystal monochromator. Q
--
W
Figure 1. ORTEP diagram of [Os(N)(CHzSiMe,)2(WS4)]-. Table I. Selected Bond Distances (A) and Angles (deg) for [NBun4][Os(N)(CH2SiMe&WS4] os-w oss1 os42 w s1 w s 2 OSSI-w oss2-w s 1-os-c 1 s1-ws2 Sl-W-S3
2.8970(5) 2.343(3) 2.349(4) 2.238(3) 2.244(3) 78.4( 1) 78.2(1) 82.4(3) 103.7(1) 111.4(1)
OS-N 1 os-c 1 Os-C5 w s 3 w s 4 N1-OS-C5 Nl-Os-Cl s2-0s-c1 s1-0ss2 SI-WS4
1.62( 1) 2.13(1) 2.11(1) 2.132(4) 2.128(4) 102.6(5) 102.3(5) 148.1(3) 97.3(1) 109.6( 1)
Table 11. Selected Bond Lengths (A) and Angles (deg) for [(M~~S~CHZ)~OS(N)IZ(~-WS~) Osl-w os2-w OSlSl os142 Os243 Os244 w s 1 w s 2 OSlSl-w OslS2-w 0~2S3-W os2s4-w SI-ws2 S1-WS3 SI-WS4
2.8372(4) 2.837 3(4) 2.367(2) 2.357(2) 2.366(2) 2.366(2) 2.204(2) 2.214(2) 76.63(6) 76.66( 6) 76.46(6) 76.52(6) 107.03(7) 110.24(7) 112.26(7)
Osl-Nl Os2-N2 Osl-c1 Osl-C5 0~2-C9 0 ~ 2 - C13 w s 3 w s 4 Nl-Osl-CS N 1-08 1-C 1 S1-Osl-C1 S2-0~l-C5 SI-Os142 0~1-W-0~2 S3-WS4
1.617(6) 1.63l(6) 2.140(6) 2.133(6) 2.130(6) 2.145(7) 2.2 15(2) 2.212(2) 104.4(3) 102.4(3) 150.3(2) 146.3(2) 97.49(6) 166.21(1) 106.70(7)
molecular structure was determined by X-ray diffraction on yellow, transparent crystals that were obtained by slowly evaporating a methylene chloride solution of 4 a t room temperature. Selected bond distances and angles are presented in Table 11,and crystallographicdata are given in Table 111. The complex contains two osmium centers (Figure 2), in which each osmium is bound to two alkyl groups, the nitride, and two sulfur atoms of the bridging tetrathiotungstate. The geometry around both osmium centers is distorted square pyramidal, with the metals above the plane of the four basal ligands; and that around tungsten metal is distorted tetrahedral with S-W-S angles between 106.70(7) and 112.26(7)O. The tungsten-sulfur bond distances
W
Figure 2. ORTEP diagram of OSZ(N)~(CH~S~M~~)~(WS~).
are similar, ranging from 2.204(2) to 2.215(2) A. The osmiumtungsten distances are shorter than the covalent Os-W distance of 3.140 A. Reaction Chemistry of [NB~~IOS(N)(CH~~~M~~)Z(WS~)~ and [Os(N)(CH2SiMea)~Cl]~(p-WS4). The neutral trimetallic complexreacts withchloride togiveanaddition product. Theaddition of 2 equiv of tetraphenylphosphonium chloride to a methylene chloride solution of compound 4 gave a gold-colored solution. Analytically pure, yellow crystals of [PPh,] z[%Osz(N)zClzWS4] (5) were collected from methylene chloride/hexane solution in 62% yield. The IR spectrum of 5 included strong bands at 1103 and 528 cm-1, assigned to the osmium-nitride and tungstensulfide stretching vibrations. The N M R spectra of 5 show that the alkyl groups are equivalent. The negative-ion FAB-MS showed an intense peak at m l z = 1480 that corresponds to [PPhd] [ R ~ O S ~ ( N ) Z C ~ ~and W Sa ~band ] , at 372 nm in the visible spectrum is associated with the tetrathiotungstate ligand. The bimetallic complex [NBu4] [Os(N)(CHzSiMe3)2( WS4)] does not react with tetraphenylphosphonium chloride. It does react with excess aqueous hydrochloric acid to give [NBu4][Os(N)(CH2SiMe3)2Clz]. Neither 1 nor 4 reacts with carbon monoxide, hydrogen, ethylene, pyridine, or elemental sulfur. There is no reaction between 1 and 1,2-ethanedithiol or benzyl alcohol. Abstraction of atomic sulfur by thiophilic nucleophiles is a reaction common to sulfido complexes and is of biochemical significance.’* The active sites of the molybdoproteins xanthine oxidase, xanthine dehydrogenase, and aldehyde oxidase possess a sulfur atom that can be abstracted by cyanide ion to yield the (18) Traill, P.R.; Tiekink, E.R. T.;O’Connor, M. J.; Snow,M. R.;Wedd, A. G.Ausf. . I Chem. . 1986.39, 1287-1295.
Osmium(V1) Complexes of Tetrathiotungstate
Inorganic Chemistry, Vol. 32, No. 25, 1993 5649
Scbeme 111
4 2-
R
R 5
thiocyanate ion and an inactive form of the e n ~ y m e . 1Trime~ thylphosphine reacted with both 1 and 4 over several hours at room temperature in benzene to give trimethylphosphine sulfide. The phosphine sulfide was characterized by lH and 31PNMR, mass spectroscopy, and gas chromatography. We were unable to isolate the organometallic products in either reaction. (Under other reaction conditions, PMe3 reduced the osmium center in 1.I7) Neither [NBu4] [Os(N)(CH2SiMe3)2( WS4)] nor [Os(N)(CH2SiMe3)2Cl]2(pWS4) reacted with triphenylphosphine.
Discussion Tetrathiotungstate and tetrathiomolybdate are electron-rich, chelating ligands that readily displace chloride from the osmium center in organometallic nitridoosmium complexes. On the basis of spectroscopicdata, these ligands are better donors than chloride but are less electron-donating than alkanethiolate ligands. The osmium-nitrogen stretch, which correlates inversely with electron density of the metal, is 1124 cm-l for [NBud] [cis-Os(N)(CH2SiMe3)$12], 1091 cm-' for [NBud] [Os(N)(CH2SiMe3)2(SCH2CH2S)],20and1 105 cm-1 for [NBu4] [Os(N)(CH2SiMe3)2(WS4)]. The nitrogen-osmium triple bond stretch can be similarly compared for the neutral osmium complexes: 1128 cm-' for [ O S ( N ) ( C H ~ S ~ M ~ and ~ ) ~1102 C ~ ] cm-1 ~ ~ ~ for [Os(N)(CHzSiMe3)212(WS4). A comparison of the IR and NMR spectra of [NBu4] [Os(N)(CH2SiMe3)2(WS4)] and [NBu4][Os(N) (CH2SiMe3)z(M&)] shows that the tetrathiomolybdate and tetrathiotungstate groups are essentially identical in their ability to donate electron density to the osmium center. The bond lengths and angles of the Os(N)(CH2SiMe& units in 1and 4 are very similar those of the square pyramidal complex [NBu4][ Os(N) (CHzSiMe3)rj .22 The osmium-nitrogen distance in the tetraalkyl complex (1.63 1( 1) A) compares with the Os-N distances in 1 (1.62(1) A) and in 3 (1.617(6) and 1.631(6) A). The tungsten center has a slightly distorted tetrahedral geometry in [NBu4] [Os(N)(CH2SiMe3)2(WS,)] with short terminal W S distances of 2.132(1) and 2.128(4) A and longer bridging WSdistancesof 2.238(3) and2.244(3) A. The terminal W S distancesareshorter than thosefoundin (NH4)2WS4(2.165 A average)23and (p-cymene)Ru(PPh3)WS4 (2.153 A average).8 Comparably short terminal M S (M = Mo, W) distances have been reported by Coucouvanis and co-workers for the anionic species [PhS)2Fe(pS)MS2]2- (M = Mo, W),Z4 by Averill and (19) (a) Massey, V.; Edmondson, D. J. Biol. Chem. 1970, 245, 6595. (b) Hille. R.; Massey, V. In Molybdenum Enzymes; Spiro, T. G., Ed.; Wiley: New York, 1985; Chapter 9. (20) Zhang, N.; Wilson, S. R.; Shapley, P. A. Organometallics 1988, 7, 1 126-1 13 1 . (21) Shusta, J. M. Ph.D. Thesis, University of Illinois, 1993. (22) Shapley, P. A.; Own, 2.Y.;Huffman, J. C. Organometallics 1986, 5, 1269-1271. (23) Sasvari, K. Acta Crystallogr. B 1963, 36, 3090. (24) Coucouvanis, D.; Strcmple, P.; Simhon, E. D.; Swenson, D.; Baenziger, N . C.; Draganijac, M.; Chan, L. T.; Simopolous, A,; Papaefthymiou, V.; Kostikas, A.; Petrouleas, V. Inorg. Chem. 1983, 22, 293-308.
co-workers for the structures of [S2Mo(~-s)~Fe(SPh)~]2and [S2Mo(~-S)2FeC12]~-,2~ and by Gamer for thestructure of [(PhS)C U ( ~ - S ) ~ M O S The ~ ] ~bridging - . ~ ~ W S distances in 1are within the normal ra11ge.892~ The O s 4 distance of 2.346 (average) is 0.06 A longer than that in [NBu"] [ O S ( N ) ( S C H ~ C H ~ C O Z ) Z ] . ~ ~ The tungsten-sulfur distances and angles in 4 are similar to those in the trimetallic complexes Cp2Ru2(MeNC)2WS4and WS4Rh2(COD).~JO The osmium-tungsten distances of 2.8970(5) A in 1 and 2.8372(4)-2.8373(4) A in 3 are all shorter than the sum of the covalent radii (3.140 A) and the OsS-W angles are acute, indicating some metal-metal interaction. The lack of reactivity of [NBun4][Os(N)(CH2SiMe9)2WS4] toward two-electron-donor molecules can be explained by the high oxidation states of both metals and the strong trans-labilizing ligands. Carbon monoxide and olefins coordinate most strongly to electron-rich, low-valent metal centers since filled, a-symmetry metal orbitals are required for metal-to-ligand back-bonding. A a-acid ligand would not be expected to bind strongly to osmium(VI) or tungsten(V1) centers. u-Donor ligands such as pyridine, thiols, and alcohols coordinate very weakly to the open coordination site of osmium in nitridoosmium(V1) alkyl complexes due to the strong trans effect of the nitrogen ligand. Similarly, ligands do not add to the tungsten because of the trans-labilizing sulfido ligands. Multiple bonding between the tungsten and sulfide ligands also stabilizes the tetrahedral geometry of the tetrathiotungstate moiety. In the neutral, trimetallic complex [(Me3SiCH2)2(N)Os]2(pWS4), the tetrathiotungstate group bridges the two osmium centers with two sulfur atoms chelating each osmium center. The addition of chloride to osmium displaces one sulfur atom to give a product with an ql;ql-tetrathiotungstatebridge, [(Me3SiCH2)22-. An (N) (Cl)Os-S-W(=S)2-S-Os(Cl)(N)(CH2SiMe3)2] alternative structure of this product with the two chloride ligands on a bridging tetrathiotungstate group, [(Me3SiCH2)2(N)(C~)OS(~S)~WC~~(~-S)~OS(C~)(N)(CH~S~M~~)~ 2-, can be discounted on the basis of the IR spectrum. The band at 528 cm-1 is in a region typical for terminal W==S stretchingvibrations and out of the range for the W-S stretch in bridging (W-S-M) tetrathiotungstatecomplexes. Addition of chloride to the osmium center if favorable because the osmium forms a strong covalent bond with chloride and loses only a weaker interaction from donation of an electron pair of a tungsten sulfide. Tungsten can form stronger a-bonds to the terminal sulfido ligands since these sulfurs are more electron rich than bridging sulfur atoms. Addition of chloride to the anionic osmium center in 1 is less favorable from an electrostatic standpoint. Also, since there are already two terminal sulfido ligands on tungsten, the displacement of a sulfur from the osmium would not promote an increase in r-bonding of sulfur to tungsten. Chloride only adds to this molecule under acidic conditions when the tetrathiotungstate moiety can be protonated. Spectroscopic data for compound 5 allow us to propose a structure for the molecule in which two trigonal bipyramidal osmium centers are bridged by an S - W S unit. The tungsten center would have two terminal sulfides along with the two bridging sulfides. The 1H NMR shows that all of the alkyl groups are equivalent. Monodentate coordination of the tetrathiotungstate to each osmium center would allow free rotation about the O s 4 bonds and equilibrium of the (trimethylsily1)methyl ligands. IR spectroscopy supports a change in bonding mode for the (25) Tieckelmann,R.H.;Silvis,H.C.;Kent,T.A.;Huynh, B.H.;Waszczak, J. V.; Teo, B. K.; Averill, B. A. J . Am. Chem. Soc. 1980, 102, 555G 5559. (26) Acott, S. R.; Garner, C. D.; Nicholson, J. R. J . Chem. Soc., Dalton Trans. 1983, 713-719. (27) Potvin, C.;Manoli, J. M.; Secheresse, F.; Marzak, S.Inorg. Chim. Acta 1990, 168, 173-177. (28) Schwab, J. J.; Wilkinson, E. C.; Wilson, S. R.; Shapley, P. A. J. Am. Chem. Soc. 1991, 113,6124-6129.
5650 Inorganic Chemistry, Vol. 32, No. 25, 1993
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SiCH3). Anal. Calcd for O S W N ~ S ~ ~ S ~ C C,~30.89; , H ~ ~H,: 6.26; N, 3.00. Found: C, 30.90; H, 6.27; N, 2.99. MS (FAB) ( m l z ) : [Os(N)(CH2SiMe3)2(WS4)]-, 692 (100%); [NBun4]+,242 (100%). Preparation of [PWIOs(N)(CH,)z(WS4)] (2). To a solution of [PPhd] [Os(N)(CH3)2C12] (0.04 g, 0.062 mmol) in 50 mL of CHiCN Conclusion was added finely ground (NH4)WSd (0.04 g, 0.124 mmol). The mixture was magnetically stirred for 24 h at room temperature and filtered, and Organometallic osmium(V1) complexes of the tetrathiotungthe filtrate was concentrated under vacuum. The residue was dissolved state anion have been prepared, isolated, and characterized. An in methylene chloride. Hexane was added, and the mixture was cooled osmium(V1) complex of tetrathiomolybdate was also synthesized. to -30 OC. Yellow crystals were collected by filtration and dried under The tetrathiotungstate group can act as a bidentate ligand for vacuum (80% yield, 0.044 9). IR (KBr pellet; cm-I): 3049-2886 (m, one osmium center. It can also bridge two osmium atoms, in YC-H), 1483 (m, CH3), 1107 (s, v"), 526 and 501 (VS,Y W - S ) 'H . either a monodentate or a bidentate coordination mode. These NMR (CD2CI2, 200 MHz, 295 K): 6 7.5-7.9 (m,10H, PPh,), 2.61 (s, complexes are thermally stable, and although they are coordi3H, OsCH,). 13C('H)NMR(CD2C12,75 MHz, 295 K): 6 130.5,130.7, natively unsaturated, they are relatively unreactive toward simple 134.4, 134.5, and 135.7 (PPh,), -1.23 (OsCH3). Anal. Calcd for O S W S ~ P N C ~ ~C,H35.26; ~ ~ : H, 2.96; N, 1.58. Found: C, 35.24; H, donor molecules. 3.03; N, 1.57. MS (FAB) ( m / z ) : [OS(N)(CHJ)~(WSI)]-,547 (67%); [NBu"~]+,339 (100%). Experimental Section Preparation of [NBIP~IO~(N)(CH@M~~)Z(M~S~)] (3). To a 100All operations were carried out under nitrogen either in a Vacuum mL round-bottomedflask were added finely ground (NH4)2McS4 (0.040 Atmospheres drybox or on a Schlenkline. Toluene,diethylether, hexane, g,O. 15mmol) and40mLof CH3CN. A solution of [NBuS] [Os(N)(CHzbenzene, and tetrahydrofuran were distilled from sodium/benzophenone SiMe3)zClzl (0.030 g, 0.043 mmol, in 5 mL of CH3CN) was added under nitrogen. Methylene chloride and acetonitrile were distilled from dropwise to the (NH4)zMoSd suspension with magnetic stirring. The CaH2. Triethylamine, pyridine-2-thiol,and 1,Zdithioethanewere distilled mixture was stirred at room temperature for 4 days and then filtered. The under nitrogen prior to use. Mg(CHzSiMe3)z was prepared from solvent was evaporated under vacuum, and the crude product was Mg(CHzSiMe3)Cl and dioxane.29 [NBQ] [ O S N C ~ ]was prepared crystallized from CHzCl~/hexaneat -30 OC. Brown crystals (0.018 g, according to Griffith.30 The compounds [NBun4][ O S ( N ) C ~ ~ R ~ ] , ~50%) ~ were obtained. IR (KBr pellet; cm-I): 2939-2864 (m, Y C - H ) , [Os(N)CI(CH2SiMe3)2],23and 1,2-bi~(diphenylphosphino)ethane~~ were 1417 (m,CH2 and CH3), 1248 (s, SiCH,), 1100 (s, YOPN),842 (vs, prepared according to literature methods. Other reagents were purchased Visible (CH2Cl2;, ,A nm (e)): 436 SiCHs), 518 and 503 (vs, YM,,-s). and used without further purification. IR spectra were obtained on a nm (5880). IH NMR (CD2C12, 300 MHz, 295 K): 6 3.14 (m, 8H, Perkin-Elmer 1600 spectrometer. NMR spectra were obtained on a NCHz), 3.01 (d, 2H, J = 10 Hz, OsCWHb), 2.59 (d, 2H, J 10 Hz, Varian XL200, General Electric QE300, or General Electric GN500 FT OsCHaHb), 1.63 (m, 8H, N C H ~ C H ~ C H ~ C H1.45 S ) , (m, 8H, NCH2NMR spectrometer. ,lP NMR spectra were recorded on a GN-300 NB CH2CH2CHa), 1.02(t, 12H,NCH2CH2CH2CH3),-0).03 (s, 18H,OsCH2instrument operating at 121 MHz. UV-visible spectra were obtained on SiCH3). 13C(1HJNMR(CD2C12,75 MHz, 295 K): 6 59.5 (NCHz), 24.4 a Hewlett-Packard Model 8450 photodiode array spectrophotometer. (NCH2CH2CH2CH,), 20.2 (NCH2CH2CH2CHa), 13.8 (NCHzCH2Gas chromatography was performed on a Hewlett-Packard Model 5790 C H Z C H ~ )6.5 , (OsCHz), 1.3 (CH2SiCH3). Anal. Calcd for A instrument with an FID detector and nitrogen as the carrier gas by OsMoNzSi2S4C24Hss: C, 33.96; H, 6.89; N, 3.30. Found: C, 34.11; H, using a 10%Carbowax 20M on Chromosorb W-HP column. The yields 6.93; N, 3.35. MS (FAB) (m/z): [ O S ( N ) ( C H ~ S M ~ ~ ) ~ ( M O604 S~,)~-, were determined by GLC relative to an internal standard. Mass spectra (29%); [NBun4]+,242 (100%). were recorded on a Finnigan MAT CH-5 (EI) or ZAB (FAB). All Preparation0f[Os(N)(CHaSiMe3)~b(rc-WS4) (4). Toa 100-mLflask analyses were performed by the University of Illinois microanalytical containing 15 mL of CH2Cl2 and 0.120 g (0.173 mmol) of [NBun,]service. Electrochemical measurements were made with a BAS 100 [Os(N)(CH2SiMe3)2C12] was added AgBF4 (0.070 g, 0.18 mmol). The electrochemicalanalyzer. All electrochemistry was done in a Vacuum color changed from orange to green to light brown. After 1 h, the mixture Atmospheres drybox. Measurements were taken on an approximately was filtered to remove AgCl and the solution taken to dryness under 0.01 M solution of the compound of interest using [NBu4][BF4] as the vacuum. The brown residue was extracted with hexane, and the extract supporting electrolyte. A solution of 0.1 M [NBud][BF4] in methylene was filtered. The solvent was removed under vacuum and the residue chloride was prepared from freshly distilled solvent. Potentials are dissolved in 20 mL of CH2C12. (NH4)2WS4 (0.040 g, 0.1 15 mmol), was reported vs Ag/AgCl. Molecular structures were determined by the added to this solution, and the mixture was stirred overnight. The color University of Illinois X-ray laboratory. changed to yellow. The mixture was filtered and solvent removed from Preparationof [NBP4IOs(N)(CHfiiMe,)Z(WS4)] (1). (NH&WS4 the filtrate under vacuum. The residue was dissolved in 5 mL of hexane (0.3 g, 0.86 mmol) was ground to a fine powder and added to a 100-mL and the solution cooled to -30 "C. The product was obtained as a yellow, round-bottomed flask along with 50 mL of CH3CN. A solution of microcrystalline powder (0.060 g, 64% yield). IR (KBr pellet; cm-I): [NBun4][Os(N)(CH2SiMe3)2C12] (0.3 g, 0.43 mmol, in 10 mL of CH32944-2889(m,vc-~), 1244(vs,SiCH3), 1 1 0 2 ( s , ~ ~ 3 4 , 8(vs,Si-C), 33 CN) was added dropwise to the (NH&WS4 suspension. The mixture 466 (s, Y W ~ )'H. NMR (CDC13, 300 MHZ, 18 "C): 6 3.67 (d, J = was stirred at room temperature under Nz for 4 days and then filtered. 10.1 Hz, lH, CWCHb), 3.58 ( d , J = 10.1 Hz, lH, CP'CH'), 3.24 (d, The solvent was removed by vacuum, and the residue was dissolved in J = 10.1 Hz, lH, CHCHb), 3.17 (d, J = 10.1 Hz, lH, CHL'CH"'), 0.10 a mixture of hexane/methylene chloride. Cooling this solution to -30 (s, 9H, Si(CH3)3), 0.063 (s, 9H, Si(CHd3). MS (FAB) ( m / z ) : 1070. OC led to the formationof yellow crytals. These were collected by filtration Anal. Calcd for C I ~ H & ~ N ~ S ~ O SC,~ 17.97; W : H, 4.15; N, 2.62. and dried under vacuum togive pure [NBun4][Os(N)(CHzSiMe3)2(WS4)] Found: C, 18.35; H, 4.21; N, 2.68. (0.38 g, 95%). IR (KBr pellet; cm-I): 2963-2889 (m, YC-H), 1469 (m, Crystauization and Reduction of X-ray Diffraction Data. Yellow 835 (vs, SiCH3), 499 CH2 and CH3), 1244 (s, SiCH3), 1105 (s, Y"), crystals of 1 suitable for X-ray crystallographic analysis were grown by nm (e)): 250 (5260), 278 (4890), (vs, YW+). UV-visible (CHzC12; A, vapor diffusion of hexane into a CHzCl2 solution and stored in CHz288 sh (4370), 373 (3010). 'H NMR (CD2C12, 300 MHz, 295 K): 6 (&/hexane under dinitrogen. The data crystal was mounted using epoxy 3.17 (d, J = 12 Hz, 2H, OsCHaHb),3.14 (m, 8H, NCHz), 2.76 (d, J = to a thin glass fiber with the (001) scattering planes roughly normal to 12Hz, 2H,0sCH8Hb), 1.62 (m,8H, N C H ~ C H ~ C H ~ C H1.45 S ) ,(m, 8H, the spindle axis on an Enraf-Nonius CAD4 automated n-axis diffracNCH~CH~CHZCHI), 1.02 (t, J = 8 Hz, 12H, NCH2CH2CH2CH3), tometer equipped with a graphite crystal monochromator (X(Mo Ka) = -0.02 (s, 18H, OsCH2Si(CH3)3). 13C('H)NMR (CD2C12, 50.3 MHz, 0.710 73 A). Data were collected at 26 OC and corrected for absorption, 295 K): b 59.40 (NCHz), 24.34 (NCH2CH2CH2CH3), 20.17 (NCHzanomalous dispersion, Lorentz, and polarization effects. The structure C H Z C H ~ C H , ) , ~ ~ . ~ ~ ( N C H ~ C H(OsCH2),1.29(CH2~ C H ~ C H ~ ) , ~ . ~ ~was solved by direct methods (SHELXS-86).33 The tungsten and osmium atom positions werededuced from a vector map. Subsequent least-squares (29) Schrock, R. R.;Fellman, J. D. J . Am. Chem. Soc. 1978, 100, 3359difference Fourier calculations revealed orientations for the remaining 3370. non-hydrogen atoms, including two disordered positions for the cation. (30) Griffith, W. P.; Pawson, D. J . Chem. SOC.,Dalton Trans. 1973, 13151320. (33) Sheldrick, G. M. SHELXS-86. In Crystallographic Compuring 3; (31) Belmonte, P. A.; Own,2.Y.J . Am. Chem.Soc. 1984,106,7493-1496. Sheldrick, G . M., Kruger, C., Goddard, R., Eds.; Oxford University (32) (a) Hewertson,W.; Watson, H. R. J . Chem.Soc. 1962,1490. (b) Carty, Press: Oxford, U.K., 1985; pp 175-189. A. J.; Harris, R. K. Chem. Commun. 1967, 235.
tetrathiotungstate moiety. The increase in the W-S stretching vibration to 528 cm-1 for 5 from 466 cm-1 for 4 indicates increased multiple-bond character.
Osmium(V1) Complexes of Tetrathiotungstate Unique positionsfor atoms C20 and C40 were never located, these atoms were constrained to one equivalent site. Anion hydrogen atoms were included as fixed contributors in "idealized" positions, and cation N-C bond lengths were constrained to be equal preceding each cycle of least squares. No other constraints were placed on the proposed model. In the final cycle of least squares, group isotropic thermal parameters were refined for the anion hydrogen atoms and the disordered cation nitrogen and carbon atoms, and anisotropic thermal coefficients were refined for the remaining atoms. Succcssful convergence was indicated by the maximum shift/error for the final cycle. The relative site occupancy for the major cation orientation converged to 0.612(2). A final analysis of variance between observed and calculated structure factors showed a slight inverse dependence on sin(t9). Yellow, X-ray-quality crystals of 4 were obtained by slow evaporation of a CHzClz solution at room temperature and stored under dinitrogen. The data crystal was mounted using epoxy to a thin glass fiber with the (231) scattering planes roughly normal to the spindle axis on an EnrafNonius CAD4 automated I-axis diffractometer equipped with a graphite crystal monochromator (X(Mo Ka) = 0.71073 A). Data were collected at -75 OC and corrected for absorption, anomalous dispersion, Lorentz, and polarization effects. The structure was solved by direct methods (SHELXS-86); correct positions for the Os and W atoms were deduced from an E map. Two cycles of least-squares refinement followed by an unweighted difference Fourier synthesis revealed positions for the remaining non-H atoms. A final analysis of variance between observed and calculated structure factors showed no systematic errors. Reaction of [Os(N)(CHfiiMe3)zh(jeWS4) with PPh&I. Synthesis of [PhShROs(N)a(CHfi~e3)~h(WS4)] (5). A solution of PPh4Cl (0.014 g, 37.4 pmol) in 5 mL of CHzClz was added dropwise to a stirred (0.020 g 18.70 pmol) in 15 solution of [OS(N)(CH~S~M~~)Z]Z(~-WS~) mL of CHzClZ. The color changed from light yellow to gold over a 12-h period. The solution was filtered, the filtrate concentrated to one-fourth the original volume and layered with an equal amount of hexane, and the mixture stored at room temperature for 3 days. Yellow, hairlike crystals were formed. These were filtered off, washed with hexane, and dried under vacuum (0.021 g, 61.76%). IR (KBr pellet; cm-I): 3049-2886 (m,vc-~), 1613,1580,and 1477 (m,Ph), 1433 (vs,.CHzandCH3), 1238 ( 8 , SiCHs), 1103 (s, Y O ~ N ) ,837 (vs, Si-C), 528 (vs, we).IH NMR
Inorganic Chemistry, Vol. 32, No. 25, 1993 5651 (CDClp, 300 MHZ, 20 "C): 6 7.93-7.61 ppm (m, 10H, P4P), 3.11 (d, J = 10.1 Hz, IH, CHLCHb),2.66 (d, J = 10.1 Hz, lH, CH*CHb),4 - 0 4 (s, 9H, Si(CH3)l). 31P(1H}NMR (CDCl3, 121 MHz, 293 K): 6 23.69. MS (FAB) ( m / z ) : 1480,(PP4)(Os(N)Cl(CH$3iMe,),),(WS4). Anal. Calcd for C ~ H g 4 P ~ C l ~ S ~ N ~ S ~C, O s42.26; 2 W : H, 4.65; N, 1.54; C1, 3.90. Found: C, 43.08; H, 4.50; N, 1.08; C1, 3.21. Renctiomof 1 and4. The osmium tetrathiotungstatecomplexes (0.01 g) were dissolved in 0.75 mL of CDCl3in a 5-mm NMR tube. Two-five equivalents of either Sg, pyridine, benzyl alcohol, ethanethiol, triphenylphosphine,or cyclohexene was added in each case. IH NMR spectra were obtained immediately after addition and again after 24 h. In all cases, only starting materials were observed. The osmium tetrathiotungstate complexes (0.01 g) were dissolved in 0.75 mL of C6D6 in a 5-mm NMR tube. One-two equivalents of PMe3 was added by microliter syringe in each case. IH and OlP NMR spectra were obtained immediately after addition, after 1 h, and again after 24 h. In each reaction, the NMR spectra showed slow consumption of the starting material and formation of S=PMe3. The osmium tetrathiotungstate complexes (0.01 g) were dissolved in 1.0 mL of CDCl3 in a medium-pressure reaction vessel. In each case, the vessel was charged with either CHf;=CHz (200 psi), Hz (lo00 psi), or CO (1000psi), and the mixture was stirred for 24 h. The gas was then discharged, and the solution was transferred to an NMR tube under N2. IH NMR spectra showed no reaction.
Acknowledgment. We gratefully acknowledge the financial support of the National Science Foundation (Grant CHE 8807707). Spectra were obtained on NMR instruments purchased through grants from the NIH and the NSF (NIH PHS 1532135, NIH 1531957, and NSF CHE 85-14500). P.A.S. gratefully acknowledges financial support from an Alfred P. Sloan Foundation Fellowship. SupplementaryMaterinlAvaihbk For [NBu][Os(N)(CH&Me3)z@S)zWS2] and [Os(N)(CHzSiMe,)z]z(WS4),tables of crystal data collection and refinement parameters, atomic coordinates, thermal parameters, and selected distances and angles (14 pages). Ordering information is given on any current masthead page.
